Power storage devices each include a plurality of secondary batteries, and can discharge power stored in the secondary batteries as necessary. For example, the power storage devices can discharge, in the daytime, power stored late at night when the electricity rate is low, and discharge, at night, power stored in the daytime by photovoltaic power generation. Also, in case of a blackout, the power storage devices can discharge power stored in the power storage devices up to that time.
Such power storage devices have often been installed in, e.g., industrial or business establishments, but, in recent years, they are beginning to be installed more in general residential houses as well.
Currently, secondary batteries used for power storage devices are generally film-package batteries. A film package battery contains battery elements formed by alternately stacking positive plates and negative plates via separators, and the battery elements and an electrolyte solution are encapsulated in a container formed of a packaging film such as a laminate film.
Patent Literature 1 describes a power storage device in which a lithium ion battery with a plurality of cells integrally packed therein is arranged in a cuboidal casing with its periphery surrounded by metal plates. The inside of the casing is separated by a wall into right and left spaces, and in one of the spaces, the lithium ion battery and a charging unit therefor are disposed. In the other space, a controller that converts power from the battery to alternate-current power and supplies the alternate-current power is disposed, and a heat dissipation space exists between the controller and the wall.
Patent Literature 2 describes a power storage system including a battery module including a plurality of battery cells and a housing case that houses the battery module, in which charge accumulated in the battery module is converted into alternate-current power and supplied to a load. The housing case has a cuboidal shape with a surface having a largest area as a front portion, and in the housing case, a plurality of the cuboidal battery modules are housed. These battery modules are arranged in such a manner that the front portion of the housing case and a surface of each battery module that has a largest area face each other, and can be inserted/removed to/from the housing case through a side portion of the housing case. Furthermore, inside the housing case, a controller that controls conversion to alternate-current power or charging/discharging of the battery modules is disposed.